DESCRIPTION; (provided by applicant): The mesoderm gives rise to a wide variety of cell types in the embryo, and plays critical roles in morphogenesis and patterning the other germ layers. Extensive evidence supports a role for Bmp and Wnt/13-catenin signaling in mesoderm formation, yet most of the targets of these factors are not known, nor is it known how these two signaling factors cooperate to regulate the formation of the posterior mesoderm. In this project, the role of these two pathways in mesoderm formation will be studied using transgenic fish that express inhibitors and activators of the Bmp and Wnt/B-catenin pathways under heat shock control. The mechanism of integration of these two pathways in the mesoderm will be studied using the tbx6 promoter, which is regulated by both Bmp and Wnt/B-catenin signals. Finally, a major part of this project is to use microarrays to determine the mesodermal genes under the combined control of the Bmp and Wnt/B-catenin pathways. Using morpholino antisense oligonucleotides, we will determine which of these genes are important for mesoderm formation, and establish a hierarchy of mesodermal genes that coordinate the patterning and formation of the mesoderm.